CLAS physics database search results Measurement E151M2944 EG4 Xiaochao Zheng 2016 cos(theta_pi+) phi(pi+) A_LU Stat. error Syst. error degrees 0.65 258 -0.2174 0.251 0.0303 0.75 90 0.1019 0.2712 0.0301 0.85 270 0.126 0.2412 0.0301